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Section: New Results

Web programming

Participants : Yoann Couillec, Vincent Prunet, Manuel Serrano [correspondant] .

Hop.js

Multitier programming languages unify within a single formalism and a single execution environment the programming of the different tiers of distributed applications. On the Web, this programming paradigm unifies the client tier, the server tier, and, when one is used, the database tier. This homogenization offers several advantages over traditional Web programming that rely on different languages and different environments for the two or three tiers of the Web application: programmers have only one language to learn, maintenance and evolution are simplified by the use of a single formalism, global static analyses are doable as a single semantics is involved, debugging and other runtime tools are more powerful as they access global informations about the execution.

The three first multitier platforms for the Web all appeared in 2006: GWT (a.k.a., Google Web Toolkit), Links, and Hop [6] , [5] . Each relied on a different programming model and languages. GWT maps the Java programming model on the Web, as it allows, Java/Swing likes programs to be compiled and executed on the Web; Links is functional language with experimental features such as the storing of the whole execution context on the client; Hop is based on the Scheme programming language. These three pioneers have open the path for the other multitier languages such as, Ocsigen for Ocaml, UrWeb, js-scala, etc.

In spite of their interesting properties, multitier languages have not become that popular on the Web. Today, only GWT is widely used in industrial applications but arguably GWT is not a fully multitier language as developing applications with GWT requires explicit JavaScript and HTML programming. This lack of popularity of other systems is likely due to their core based languages than to the programming model itself.

JavaScript is the defacto standard on the Web. Since the mid 90's, it is the language of the client-side programming and more recently, with systems like Node.js, it is also a viable solution for the server-side programming. As we are convinced by the virtues of multitier programming we have started a new project consisting of enabling multitier programming JavaScript. We have created a new language called HopScript, which is a minimalist extension of JavaScript for multitier programming, and we have implemented a brand new runtime environment called Hop.js. This environment contains a builtin Web server, on-the-fly HopScript compilers, and many runtime libraries.

HopScript is a super set of JavaScript, i.e., all JavaScript programs are legal HopScript programs. Hop.js is a compliant JavaScript execution environment as it succeeds at 99% of the Ecma 262 tests suite. The Hop.js environment also aims at Node.js compatibility. In its current version it supports about 70% of the Node.js runtime environment. In particular, it fully supports the Node.js modules, which lets Hop programs reuse existing Node.js modules as is.

After a full year of active development to enhance JavaScript and Node.js compatibility, to incorporate features of JavaScript 1.6, and to design new language constructs for machine-to-machine communication, we are now ready to release Hop.js. This will appear at the beginning of 2016.

Data source

During the past few years the volume of accumulated data has increased dramatically. New kinds of data stores have emerged as NoSQL family stores. Many modern applications now collect, analyze, and produce data from several heterogeneous sources. However implementing such applications is still difficult because of lack of appropriate tools and formalisms. We propose a solution to this problem in the context of the JavaScript programming language by extending array comprehensions. Our extension allows programmers to query data from usual stores, such as SQL databases, NoSQL databases, Semantic Web data repositories, Web pages, or even custom user defined data structures. The extension has been implemented in the Hop.js system. It has been described in the paper [10] , which has been presented at the ACM DBPL'15 conference.